To the surprise of very few, a court in Myanmar has found Nobel Peace Prize laureate Aung San Suu Kyi guilty of violating internal security laws and given a three-year prison term. As a theatrical coda to the ruling, the military regime immediately cut the sentence to 18 months of house arrest — to demonstrate its humanitarian impulses. The world must condemn this transparent attempt to sideline the most potent popular political force in Myanmar and governments must take active measures to punish those responsible.

This farce began in early May, when an American visitor, Mr. John Yettaw, swam across a lake behind Mrs. Suu Kyi's home and forced his way into her villa, claiming that God had told him she was going to be assassinated by terrorists. Mr. Yettaw, a veteran of the Vietnam war who is said to suffer from post-traumatic stress syndrome, had tried to visit Ms. Suu Kyi the previous November but was turned away at the door. This time he pled exhaustion and was permitted to sleep in the house for two days.

For that act of kindness, Ms. Suu Kyi and two women who work for her were arrested and tried for violating the terms of her house arrest and breaking a security law protecting the state from "subversive elements." Mr. Yettaw, meanwhile, was sentenced to seven years of hard labor and imprisonment.

There are plenty of reasons to be suspicious about these events. Ms. Suu Kyi's house arrest for the past six years was in itself a violation of Myanmar's laws, which limit such detention to five years. A court was to rule on her status at the end of May when Mr. Yettaw showed up. Strangely, although Ms. Suu Kyi had alerted the authorities about Mr. Yettaw's attempt to visit her the previous year, he was given another visa to visit the country.

The outcome of the trial was never in doubt. Myanmar is following its "road map to democracy," a process that is supposed to end the military junta's rule that began in 1990 when it overruled an election won by the National League of Democracy (NLD), headed by Ms. Suu Kyi. In response to international pressure — tepid, but constant — the junta agreed to give up power, but the process has been stage-managed and looks like a transition in name more than reality. NLD leaders have been imprisoned or exiled. Ms. Suu Kyi has spent 14 of the last 19 years under house arrest. NLD rallies are suppressed, their supporters harassed and jailed. That makes a mockery of the election scheduled to be held next year. In fact, it is fair to ask what the point is of a ballot that reserves a quarter of parliamentary seats for the military.

So, the court's finding that Ms. Suu Kyi and her assistants were guilty was a foregone conclusion. The intervention of Home Minister Maj. Gen Muang Oo, who announced minutes after the ruling was read that the sentence was being cut in half — because the defendant was the daughter of the country's independence hero and because of the "the need to preserve community peace and tranquillity and prevent any disturbances in the road map to democracy" — was dramatic, most particularly in the sense that it was scripted.

Ms. Suu Kyi announced she would appeal the ruling. Other governments denounced the ruling. Japanese Foreign Minister Hirofumi Nakasone said the ruling is extremely disappointing and that Ms. Suu Kyi's current conditions are extremely regrettable. United Nations Secretary General Ban Ki Moon, who was unable to meet the defendant on a recent visit to Myanmar, "deplored" the ruling. The U.N. Security Council will convene a closed-door emergency session Thursday to discuss the situation. U.S. Secretary of State Hillary Clinton said the trial should never have been held and called for the release of all political prisoners. The European Union said it will adopt additional sanctions that target "those responsible for the ruling" as well as the entire regime.

But since those governments have limited influence over the junta in Myanmar, the most important reaction is that of Southeast Asian nations. The decision to reduce the sentence was intended to send a message to them, to signal that Myanmar is sensitive to international opinion and to lessen their opposition to the trial. Singapore said it was "disappointed" by the ruling while the Philippines called the decision "incomprehensible and deplorable." That does not mean that either government, or the Association of Southeast Asian Nations (ASEAN) to which they belong, along with Myanmar, will take concrete actions to express their displeasure and press the junta to change course.

Instead, ASEAN governments are likely to continue to shelter behind the "noninterference principle" that guides ASEAN members, even though the Myanmar government's actions make a mockery of the group's commitments to democracy and human rights. They are also fearful of China further extending its influence into Myanmar. But ASEAN has shown that it has no influence over developments in the country. Only a united front among all nations that demands that the junta respect its own declared goals will bring about change and undo the latest miscarriage of justice in Myanmar.